This present invention relates generally to tandem wing aircraft and methods for manufacturing and operating such aircraft.
One goal of the commercial air transport industry is to convey passengers and cargo as quickly as possible from one point to another. Accordingly, many commercial transport aircraft operate at cruise Mach numbers of approximately 0.8-0.85. As the time constraints placed on air carriers and their customers increase, it would be advantageous to economically transport passengers and cargo at higher speeds. However, aircraft flying at transonic or supersonic speeds (greater than about Mach 0.85) have greater relative thrust requirements than comparably sized subsonic aircraft. To generate sufficient thrust at high altitudes and Mach numbers, while reducing the corresponding increase in drag, conventional transonic and supersonic aircraft include low bypass ratio turbofan engines or straight turbojet engines. Such configurations generally have a high specific fuel consumption at cruise conditions that generally outweighs any inherent advantage in aerodynamic efficiency, resulting in a net fuel efficiency significantly lower than that of lower speed aircraft. The low fuel efficiency can also result in increased atmospheric emissions.
FIGS. 1A and 1B illustrate top isometric and bottom isometric views, respectively, of a supersonic cruise aircraft 10a in accordance with the prior art. The aircraft 10a can include a fuselage 13a, a delta wing 12a, a propulsion system 15a suspended from the wing 12a, and an aft-tailed pitch control arrangement 17. Alternatively, the aircraft 10a can include a tail-less or canard pitch arrangement. In either configuration, the longitudinal distribution of the exposed cross-sectional area of the aircraft, and the longitudinal distribution of the planform area tend to dominate the transonic and supersonic wave drag (i.e., the increase in drag experienced beyond about Mach 0.85 due to air compressibility effects). Accordingly, the fuselage 13a can be long, thin, and xe2x80x9carea-ruledxe2x80x9d to reduce the effects of wave drag at supersonic speeds.
Area-ruling the fuselage 13a can result in a fuselage mid-region that is narrower than the forward and aft portions of the fuselage (i.e., a xe2x80x9cwaistedxe2x80x9d configuration). Waisting the fuselage can compensate for the increased cross-sectional area resulting from the presence of the wing 12a and the propulsion system 15a. The propulsion system 15a can include four engine nacelle pods 16a mounted beneath the wing 12a to minimize adverse aerodynamic interference drag and to separate the rotating machinery of the engines from the main wing spar and the fuel tanks located in the wing. Noise suppressor nozzles 18a are typically cantilevered well beyond a trailing edge of the wing 12a, and can accordingly result in large cantilever loads on the wing 12a. 
FIGS. 1C-E illustrate a side view, plan view and fuselage cross-sectional view, respectively, of a configuration for a high-speed transonic cruise transport aircraft 10b having a fuselage 13b, a swept wing 12b, and engine nacelles 16b suspended from the wing 12b in accordance with the prior art. The fuselage 13b has a significantly narrowed or waisted portion proximate to a wing/body junction 19. Accordingly, the fuselage 13b is configured to avoid or at least reduce increased drag in a manner generally similar to that described above with reference to FIGS. 1A and 1B. This configuration may suffer from several drawbacks, including increased structural weight, increased risk of flutter loads, and a reduced payload capacity. The configurations shown in FIGS. 1A-1E can be structurally inefficient and can have reduced payload capacities as a result of the fuselage waisting required to reduce transonic and supersonic drag.
The present invention is directed toward tandem wing aircraft and methods for manufacturing and operating such aircraft. An aircraft in accordance with one aspect of the invention includes a fuselage having a first portion and a second portion projecting upwardly from the first portion. The first portion houses a passenger deck and the second portion is positioned above the passenger deck. A first wing extends outwardly from the first portion of the fuselage and a second wing extends outwardly from the second portion of the fuselage. The second wing is positioned above and forward of the first wing.
In a further aspect of the invention, the fuselage can include a plurality of passenger doors simultaneously accessible to ground-based passenger load/unload equipment. At least one of the passenger doors is positioned beneath the second wing. In still further aspect of the invention, the aircraft can have a forward portion, an aft portion, and an intermediate portion between the forward and aft portions, with a cross-sectional area distribution of the aircraft increasing at least approximately monotonically from the forward portion to the intermediate portion, and decreasing at least approximately monotonically from the intermediate portion to the aft portion.
The invention is also directed toward a method for loading and unloading an aircraft and includes positioning a first passenger load/unload device adjacent to a first passenger door of the aircraft, with the aircraft having a first wing and a second wing positioned forward of and above the first wing. The method can further include positioning a second passenger load/unload device adjacent to a second passenger door of the aircraft while the second passenger load/unload device is positioned beneath the second wing of the aircraft and while the first passenger load/unload device is positioned adjacent to the first passenger door. The method can still further include simultaneously moving passengers through both the first and second passenger doors.
The invention is still further directed to a method for manufacturing an aircraft. The method can include providing a fuselage having a first portion and a second portion projecting upwardly from the first portion, with the first portion housing a passenger deck and the second portion being positioned above the passenger deck. The method can further include mounting a first wing to the first portion of the fuselage and mounting a second wing to the second portion of the fuselage with the second wing being positioned above and forward of the first wing. In a further aspect of the invention, the method can further include providing the fuselage with a plurality of passenger doors that are simultaneously accessible to ground-based passenger load/unload equipment, with at least one of the passenger doors being positioned beneath the second wing.